1. Field of the Invention
The present general inventive concept relates to an ink jet head substrate, an ink jet head, and a method of manufacturing the ink jet head substrate, and more particularly, to an ink jet head substrate provided with a plurality of segment heaters that heat the substrate, an ink jet head provided with the ink jet head substrate, and a method of manufacturing the ink jet head substrate.
2. Description of the Related Art
A thermal ink jet head typically uses a plurality of heat-generating resistors as an electro-thermal transducer on a substrate to create bubbles by instantly heating ink, thereby ejecting ink droplets from the ink jet head. The plurality of heat-generating resistors are located in ink chambers, in which the ink is temporarily stored, before heating. The ink in the ink chambers is ejected by the pressure generated by the heat-generating resistors onto a recording medium through a nozzle that is in fluid communication with the ink chambers.
The temperature of the substrate on which the ink jet head is manufactured affects performance of the ink jet head. That is, when the temperature of the substrate is lower than an ambient temperature, the ink may not be ejected until the temperature of the substrate exceeds a predetermined temperature. In addition, when the temperature of the substrate reaches a high level, a size of the ejected ink droplets increases due to a decrease of ink viscosity and changes in the physical properties of the ink. An increase in the size of the ink droplets causes deterioration in the quality of a printed image. When the temperature of the substrate reaches a higher level, the nozzle may become temporarily incapable of ejecting the ink droplets due to the bubbles generated in the nozzle. The ink may be burned out. Therefore, the temperature of the substrate should be precisely controlled. To this end, a temperature sensor for detecting the temperature of the substrate and a substrate heater for heating the substrate are formed at a predetermined region of the substrate.
An ink jet head substrate provided with temperature sensors and substrate heaters is disclosed in U.S. Pat. No. 5,175,565 to Ishinaga et al., entitled “Ink jet Substrate Including Plural Temperature Sensors And Heaters.” According to U.S. Pat. No. 5,175,565, the temperature sensors use a heat resistant device, such as a diode or a transistor. The temperature sensors are disposed at both ends of the ink jet head substrate, and the heaters for heating the ink jet head substrate are disposed at remaining parts of both ends of the ink jet head substrate. In addition, an ink ejection region including heat-generating resistors for generating heat energy for ink ejection is provided on the ink jet head substrate between the heaters. When the temperature of the ink jet head substrate is low, the heaters are operated to heat the ink jet head substrate to an appropriate temperature according to the temperature detected from the temperature sensors. In addition, when the temperature of the ink jet head substrate is abnormally high, a printing operation is stopped until the temperature of the ink jet head substrate decreases to an appropriate temperature.
According to U.S. Pat. No. 5,175,565, the heaters are formed by the same process and of the same material layer as the heat-generating resistors. The process may include forming a high resistance metal layer and a metal wiring layer on the substrate, patterning the high resistance metal layer and the metal wiring layer to form a wiring pattern, and partially removing the metal wiring layer of the wiring pattern to expose a predetermined region of the high resistance metal layer. The metal wiring layer is partially removed by photo and wet etching processes. By partially removing the metal wiring layer, the heat-generating resistors are formed at the ink ejection region, and the substrate heaters are formed at both ends of the ink ejection region, simultaneously. The heat-generating resistors and the substrate heaters are the exposed regions of the high resistance metal layer.
However, the substrate heaters are typically formed to have an area wider than that of the heat-generating resistors in order to heat the entire ink jet head substrate. Therefore, a problem may occur when the heat-generating resistors and the substrate heaters are exposed by the same wet etching process as described above. That is, when the wet etching process is performed based on the area of the heat-generating resistors, the substrate heaters having an area wider than that of the heat-generating resistors may not be sufficiently exposed. As a result, the substrate heaters may not perform inherent functions. In addition, when the process of exposing the heat-generating resistors and the wet etching process of exposing the heaters are separately performed, the process becomes overly complicated.
Furthermore, the heaters are formed at both ends of the ink jet head substrate. Therefore, it may be difficult to uniformly heat the entire ink jet head substrate, and especially, to uniformly control the temperature of the ink jet head substrate in the ink ejection region where the ink is actually ejected.